Once I was old enough to think about what I was saying I vaguely had the idea that the phrase "Indian Giver" referred to the way white people cheated Indians. Like, that they would break treaties etc. It was relatively late when I thought oh wait--maybe it's an incredibly hypocritical insult to Native Americans, saying they were basically demanding do-overs to fair deals. I've never read the history of the phrase, but now I assume that's what it is.

What's unfortunate about some of these phrases is they're so useful not as racist insults but as descriptions. I've never connected the phrase "welshing on a deal" to Wales until this moment (I assume you know that's where it comes from) but I can see why the phrase gets used, because it's the correct descriptor to a certain behavior that's just not exclusive to Welshmen. Same with Indian Giver. Probably gyp as well.

I guess whether something continues probably is a combination of the attitudes and how useful the word is. It's like the way so many American phrases comes from gambling, with the literal gambling meaning and sometimes even the original game is completely lost.